Assimilation of new Latin American immigrants in the U.S. is examined in a longitudinal framework. Mexican immigrants and Cuba emigres, comprising the first and third major national contingents of immigration in recent years, were selected as targets. Samples from both groups were interviewed at entry points in Miami and in Laredo and El Paso during 1973-74. Current plans call for re-interviews during mid-1975 and mid-1977. Initial interviewing aimed at establishing a base line of objective and subjective background factors with which immigrants arrive. Aspirations and expectations for life in the U.S. were also assessed. Subsequent interviewing will aim at measuring different facets of assimilation and establishing the causal impact of background and social contextual factors on them. Structural assimilation -- entry and movement into the occupation, income, and other status hierarchies of U.S. society; cultural assimilation -- changes in language usage, values, norms, and self-identities; and communal assimilation -- relative acceptance of immigrants into formal groups and primary relationships of the receiving society -- will be examined. Sample sizes are 805 for Mexican respondents and 500 for Cubans. Reports based on the initial data will be available by the end of 1974.